This study evaluates whether there is an interaction between etonogestrel, the progestin hormone released by the contraceptive implant Nexplanon, and efavirenz, a common medication used to treat HIV. The endpoints measured in this study will help determine if such an interaction leads to decreased contraceptive efficacy of the contraceptive implant.

Serum concentration of etonogestrel before and after two weeks of efavirenz [ Time Frame: 6 weeks ] [ Designated as safety issue: No ]

We will draw a baseline serum etonogestrel immediately prior to a participant starting the 2-week course of efavirenz. Serial blood samples will subsequently be drawn over the next 6 weeks to assess for changes in serum etonogestrel concentration. We will be looking to see if the serum etonogestrel concentration decreases below the level necessary for reliable ovulation suppression.

Secondary Outcome Measures:

Serum efavirenz concentrations at the start and end of the 2-week dosing period [ Time Frame: 2 weeks ] [ Designated as safety issue: No ]

We will assess serum efavirenz concentrations at the beginning and end of the 2-week dosing period. By comparing these concentrations to historical controls, we will determine whether taking efavirenz while using the etonogestrel implant alters the serum concentration of efavirenz.

We will test serial blood samples for levels of luteinizing hormone (LH), follicle stimulating hormone (FSH), estradiol, and progesterone to determine whether the etonogestrel implant is able to suppress ovulation during and after a course of efavirenz.

For the entire 6 week period of the study, participants will undergo twice-weekly transvaginal ultrasound to assess for the development of ovarian follicles. This direct assessment of follicular development will be combined with serum hormone concentrations to determine if efavirenz increases the incidence of ovulation in women using the etonogestrel implant for contraception.

Cervical mucus quality will be assessed twice weekly throughout the study period. The etonogestrel implant exerts a secondary contraceptive effect by causing cervical mucus to become thick and sticky, and therefore less permissive to the movement of sperm through the female genital tract. We will assess whether efavirenz causes a change in cervical mucus quality that would make sperm penetration more likely, and therefore indicate a reduction in the implant's contraceptive effect.

Healthy, reproductive-age women using the etonogestrel contraceptive implant who will take a two-week course of efavirenz 400 mg orally each night.

Drug: Efavirenz

Healthy women who are using Nexplanon will be asked to take a 2-week course of reduced-dose efavirenz (400 mg daily).

Other Name: Sustiva

Detailed Description:

Women now make up nearly half of the world's HIV-infected population, and many of these women with HIV are of reproductive age. There is a growing need to provide effective contraception for those women who want or need to be protected against pregnancy. However, there is concern for decreased contraceptive efficacy in women on antiretroviral therapy who rely on hormonal contraception due to drug-drug interactions. Of particular concern is a possible interaction with etonogestrel, the active hormone in a long-acting reversible contraceptive implant. We propose a pilot study to evaluate the effect of efavirenz (EFV), a commonly used non-nucleoside reverse transcriptase inhibitor, on the pharmacokinetics of the etonogestrel implant. We will recruit 18 healthy women who have had the implant in place for 12 to 24 months. They will be asked to take a two-week course of efavirenz. During these two weeks and for four additional weeks, we will monitor semi-weekly etonogestrel concentrations, and serum, ultrasound, and cervical mucus markers of ovulation. We will also assess efavirenz concentration at baseline and at the end of the two-week treatment course. We will derive pharmacokinetic parameters and compare concentrations across time points. Results will help to inform the design of larger studies, and of similar studies with different antiretroviral medications. We hypothesize that taking efavirenz while using the etonogestrel contraceptive implant will not result in an increased incidence of ovulation.

Eligibility

Ages Eligible for Study:

18 Years to 40 Years (Adult)

Genders Eligible for Study:

Female

Accepts Healthy Volunteers:

Yes

Criteria

Inclusion Criteria:

Healthy women aged 18-40 years who have a Nexplanon®/Implanon® in place that is palpable on exam, had the device placed between 12 and 24 months prior to enrollment, and can provide documentation of when the implant was placed

Agree to use an additional reliable method of contraception while participating in the study. Acceptable methods include:

Abstinence

Condoms (male or female) with or without spermicide

Pre-existing sterilization of subject or her male partner

Willingness to abstain from alcohol consumption during the study period

Willingness to abstain from any grapefruit product or supplement for the duration of the study.

Exclusion Criteria:

Breastfeeding

Hypersensitivity to efavirenz

History of seizure disorder

Initiated, discontinued, or changed doses of drugs that are cytochrome P450 isoenzyme 3A4 (CYP3A4) inducers or inhibitors within 30 days of study entry.

Contacts and Locations

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To learn more about this study, you or your doctor may contact the study research staff using the Contacts provided below.
For general information, see Learn About Clinical Studies.

Please refer to this study by its ClinicalTrials.gov identifier: NCT01980342